The invention relates to a device for actively reducing sound transmission, provided with a first and a second wall enclosing an inner space, wherein at least the second wall is provided with actuators, for instance electromagnetic actuators and/or piezoelectric elements.
Such a device is known from practice, in particular in the form of a sound transmission-reducing panel, and is, for instance, described in international patent application WO94/05005. The device may, for instance, be used to reduce disturbing sounds from sound-producing parts of machines, buildings, vehicles, vessels, aircraft and the like. The known device may, for instance, be placed between two spaces in order to actively reduce sound coming from one space such that as little of that sound as possible can reach an adjacent space. For this purpose, the actuators of the device can produce so-called anti-sound.
It is noted that, for the device according to the opening paragraph, sound reduction in a space in which, for instance, a strong sound source is present is not of primary importance. Thus, the device according to the opening paragraph is to be distinguished from sound-absorbing devices known from practice which are set up along a space in order to absorb a sound pressure prevailing in that same space.
The device known from practice is provided with actuators, for instance electromagnetic actuators, piezoelectric elements and the like, to actively reduce sound transmission. During use, such actuators are usually connected to an electronic control, for instance a computer or the like, to make these actuators carry out those movements by means of which sound transmission reduction is effected. The reduction of sound transmission by means of actuators is known to a skilled person and is, for instance, described in the international application WO 94/05005 referred to hereinabove, which document is considered inserted in the present application by reference. Because at least the second wall is provided with actuators, in particular, a good reduction of the transmission of low-frequency sound can be achieved.
A disadvantage of the known device is that, for a desired good sound transmission reduction, it needs to be provided with relatively heavy, complex and expensive electronics and actuators. In addition, the known device consumes relatively much energy in order to achieve a desired sound reduction. Thus, use of the known device in cases in which relatively little energy is available, for instance when the energy is obtained from a battery and/or natural energy sources such as solar and/or wind energy, is not possible or not profitable. In addition, because of the high energy consumption, the known device is relatively expensive in use.